1. Field of the Invention
The present invention relates to an apparatus and method for detecting an adjacent object, and a method of driving an electronic device.
2. Discussion of Related Art
Sensing methods currently used in touch screens are mainly based on resistive layer sensing, surface acoustic wave (SAW) sensing, and capacitive sensing. Among the sensing methods, capacitive sensing enables multi-touch sensing and has excellent durability, recognizability, etc., thus being selected as a main input means of portable mobile devices.
A capacitive touch screen senses a change in the amount of charge in capacitive sensors on a touch screen panel caused by a user, thereby recognizing a user input. According to charge accumulation methods, capacitive touch screens are classified into a self-capacitive touch screen and a mutual-capacitive touch screen. In the self-capacitive touch screen, each conductor constitutes one capacitive sensor to form a reference ground or an electrified surface outside a touch screen panel, whereas, in the mutual-capacitive touch screen, two conductors on a touch screen panel constitute opposite electrified surfaces and function as one capacitive sensor.
In a general self-capacitive touch screen, an orthogonal X/Y conductor disposition is used. In this case, each capacitive sensor functions as a line sensor, and thus upon sense of each touch screen, receives only one piece of X-sensing information and one piece of Y-sensing information from an X-line sensor group and a Y-line sensor group, respectively. Therefore, the general self-capacitive touch screen is capable of sensing and tracking a single touch but cannot support multiple touches. Also in a mutual-capacitive touch screen, the orthogonal X/Y conductor disposition is used. However, the mutual-capacitive touch screen differs from the self-capacitive touch screen in that each capacitive sensor is configured in the form of a grid sensor at each position where conductors cross at right angles, and reactions of all grid sensors are separately sensed upon detection of a user input on the touch screen. Since grid sensors correspond to different pairs of X/Y coordinates respectively and provide separate reactions, the mutual-capacitive touch screen may sense and track multiple touches of a user by extracting user input information from a set of X/Y-sensing information received from the set of X/Y grid sensors.
A conductor configuration and a sensing method of a general mutual-capacitive touch screen panel are as follows. First electrodes consisting of conductors extending in one direction and second electrodes consisting of conductors extending in a direction perpendicular to the first electrodes form mutual-capacitive sensors using a dielectric material between the first and second electrodes as a medium. When the distance between first and second electrodes of each pair is d, the area of each electrified surface is a, and the equivalent permittivity of all dielectric materials between electrified surfaces is ∈, a capacitance C of each of the sensors is defined as C=∈*a/d and has a relationship with an amount Q of charge accumulated in the sensor and a potential difference (voltage) V applied to the two electrodes/electrified surfaces as Q=CV. When a user approaches a sensor, interference occurs in an electric field formed between two electrodes and hinders charge from being accumulated in the sensor. Then, the amount of charge accumulated in the sensor is reduced, and as a result, the capacitance of the sensor is reduced. This may be understood as a change of the capacitance resulting from a change in the equivalent permittivity between electrified surfaces caused by approach of the user, but there is actually a physical phenomenon that a part of an electric field between the electrified surfaces is shunted and thus the amount of electrification/accumulated charge is reduced. When an alternating current (AC) voltage source is connected to the first electrode and an AC waveform is applied to one electrified surface, a change ΔQ in the amount of electrification corresponding to ΔQ=CΔV occurs with respect to C that varies according to the degree of approach of the user, and is converted into a current or voltage by a read-out circuit connected to the second electrode. Information converted in this way is generally subjected to signal processing operations, such as noise filtering, demodulation, analog-to-digital conversion, and accumulation, and then is used in a coordinate tracking algorithm and a gesture recognition algorithm. As a preceding patent relating to such a capacitive touch-sensitive panel, there is U.S. Pat. No. 7,920,129.
According to an existing apparatus and method for detecting an adjacent object, a signal processing operation of an active mode for detecting touch input coordinates and touch strength is performed as is even in an idle mode for waiting for an input of a user. However, when signals are processed in the idle mode for waiting for a touch of a user to switch to the active mode in the same way as in the active mode for detecting touch coordinates and touch strength of a user, unnecessary power consumption increases. By lengthening a refresh rate that is a period for detecting touch coordinates and touch strength, it is possible to reduce power consumption. However, when the refresh rate lengthens, a latency that is a time interval between the moment a touch is made to use a device in the idle mode and the moment the device enters the active mode and reacts lengthens, and reactions to a touch input of a user deteriorate.
To solve this problem, the latency can be reduced by separately configuring driving structures for the active mode and the idle mode. However, the introduction of an additional circuit for the two driving structures leads to an increase in the area of a chip, which goes against the trend of miniaturization and slimness, and may also lead to an increase in unnecessary power consumption.